SmarTrunk Systems ST-9116C, Service Manual, Page: 13 / 67

ST-9116C SM R 1.1 SMARTRUNK SYSTEMS, INC. 13
4.3.6. AUTOMATIC TRANSMIT POWER
CONTROL
The RF power detector (U1) detects
transmitted feedback and reverse
power feedback, and then the
detected signals are send to power
control stage (U9) to be compared
with the referenced power control
coming from TX audio processor
(U20). The reference power level are
set by the main processor (U37) to
the audio processor (U20) in agree
to the current channel information
stored into the memory.
Power control stage (U9) also
compares
the reverse power
feedback coming from power meter
bridge (U1) to protect the power
module in case of antenna
mismatching.
The output of the power control
stage (U9) is fed direct to the RF
power Amplifier (U3) controlling the
DC bias input of the hybrid module.
Evenly when power level is adjusted
by software on three levels (Hi, Med,
Lo) the power value can be adjusted
to any desired value between zero
and 50Watts by the alignment
software.